1. Field of the Invention
The present invention relates to an image sensor, and more particularly, to an image sensor which includes a light emitting diode (LED) having a wavelength of 650 nm or a wavelength band of 610 nm to 650 nm and an illuminance sensor section having illuminance sensors and red pixels such that an illuminance can be measured and photographing can be easily implemented without loss of image quality in a night-photographing mode or a proximity measurement mode.
2. Description of the Related Art
In order to overcome the disadvantages of a general CCD (charge-coupled device) camera, an infrared (IR) CCD camera capable of photographing a subject even at night using an IR illumination device has been disclosed in the art. Recently, the IR CCD camera is gaining popularity as a surveillance camera because it can photograph an image up to an IR wavelength band which is invisible to human eyes so that photographing a subject is possible not only in the daytime but also at night.
An image sensor employing a CCD or a CMOS (complementary metal oxide semiconductor) has an absorption band of 400 nm to 1,100 nm. In general, visible rays have a wavelength band of 380 nm to 650 nm, and infrared rays have a wavelength band of about 650 nm to 1,100 nm. In order to display colors, an IR cutoff filter (which passes light rays having a wavelength band below 650 nm and cuts off light rays having a wavelength band over 650 nm) is used so as to sense the same colors that are perceived by a person. In the image sensor, in order to photograph a subject at night with weak external light, the following two methods are generally used.
In a first method, the IR cutoff filter is mechanically removed at night, and an LED having an IR wavelength band (mainly of 850 nm) is turned on. In a second method, the properties of the IR cutoff filter are set to pass only a specified IR wavelength band (mainly of 850 nm), and an LED having a certain wavelength band (mainly of 850 nm) is externally used as an illumination source.
However, in the first method, since a device for mechanically moving the IR cutoff filter is needed, a problem is caused in that the manufacturing cost increases. In the second method, even though the device for mechanically moving the IR cutoff filter is not needed, as the light rays of 850 nm pass through the IR cutoff filter in the daytime, a problem is caused in that the qualities of colors are likely to be degraded.
Meanwhile, a proximity measurement function is used in such a way as to measure how far a human body, etc. is away from an image sensor (or a mobile terminal), and to intercept power supply to a back light unit (BLU) of an LCD (liquid crystal display) when the human body is close to the image sensor (for example, while talking over the mobile terminal) so as to reduce power consumption or to interrupt the operation of a touch sensor so as to prevent mis-operation thereof. Recently, the proximity measurement function is increasingly demanded in the art.
In the conventional art, the proximity measurement function is achieved by an LED and a light receiving element. In general, a proximity sensor is separately manufactured and is mounted to the mobile terminal, and so forth.
An illuminance measurement function is realized as a device for measuring the brightness of external light in a mobile terminal. In the case where the brightness of external light is substantial, the brightness of a display unit of the mobile terminal is elevated so that the readability of displayed information can be improved, and in the case where the brightness of external light is insufficient, the brightness of the display unit of the mobile terminal is lowered so that glaringness is prevented and power consumption can be reduced. In general, in order to provide the illuminance measurement function, an illuminance sensor is mounted separately from the image sensor.